All Genetic Epidemiology Branch investigations evaluate the contributions of host susceptibility and environmental exposure in the development of cancer. A broad range of study designs are utilized, varying from family studies for linkage analysis, to biochemical epidemiology studies, to more classical case-control and cohort studies. A number of new investigations were initiated this year, including an extension of the melanoma case- control study to evaluate the familiarity of dysplastic nevi; interdisciplinary studies of breast, prostate and bladder cancers; and cohort studies to assess risk of second cancers after Hodgkin's disease, epipodophyllotoxin exposure, and small cell lung cancer. In addition, a formal agreement with the Laboratory of Viral Carcinogenesis for gene mapping was developed to replace a previous contract.